Acoustic diaphragm and loud-speaker combination



J1me 1930- N. BALDWIN 1,761,100

ACOUSTIC DIAPHRAGM AND LOUD SPEAKER COMBINATION Filed Jan, 23, 1926 BM INvE Patented June 3, p 1930 UNITED STATES NATHANIEL BALDWIN, E Ea s'r 'MILL CREEK, mm

ACOUSTIC DIAPHRAGM AND LOUD-SPEA KER COMBINATION Application filed January 28, 1926. Serial No. 83,297.

acoustic diaphragms andparticularly to that class in which large diaphragms are used without horns for loud speakers.

The principal object of the. invention is to produce a diaphragm which is extremely light, delicate, and sensitive and yet forcefully responsive throughout to the impulses communicated to it.

I attain this and other objects by the mechanism illustrated in the accompanying drawing in which the figure is a section of the instrument showing the essentials of the construction.

In the figure numeral 1 designates the housing which may be made in the form of a cylinder. Numeral 2 designates a ring which is securedvto the inner surface of the housing 1, and at its inner circumference is provided with a projecting flange 3, which forms a seat for the diaphragm. The dia-v phragm 4 made of paper or other like membranous material has a special curvature as shown andis adapted to withstand pneumatic pressure or vacuum within the housing 1; and the excess pressure against the diaphragm is counterbalanced by stress on the connecting link 5 which may be a rodor a cord and the stress may be either pressure or tension according to which side of the diaphragm sustains the excess pressure.

The edge of the diaphragm is provided with a re-enforcing rim 6 made of a folded strip of metal or other suitable material. The rim 6 is somewhat larger in diameter than the flange 3, and when the diaphragm is placed against the flange'3 and force is applied to the rim 6 to press the diaphragm against the flange the diaphragm will be put under tension and also held in airtight contact with the flange 3. A suitable force' against the rim 6 and uniformly distributed around it is obtained by means of an expansible ring 7, preferably a compressed spiral spring, which presses against an inclined surface 8 on one side of an annular groove formed in the inner wall of the housing 1 and against said rim. The housing may be conveniently made of sheet metal,

in which case the groove will consist of an annular bead in the material.

The desired pressure within the housing, either greater or less than atmospheric pressure, may be obtained and regulated in any suitable manner but in the mechanism here illustrated an inflating pressure is obtainedv by means of a bulb pump 9 and held a proximately uniform by means of a weig t 10 resting upon the flexible membrane 11 which closes the upper end of the housing 1. This membrane 11, which may be made of soft rubber, ismounted within the housing by-means of a ring 12, flange 13, rim 14, expansible ring 15 and inclined surface 16 in the same manner as described in relation to the diaphra m.

Numeral 17 designates a lever actuated by a spring 18 and pressing upward against the 7 central portion of the membrane 11 and so arranged that when the weight 10 is lifted to the proper. height by means of the ump 9 the lever 17 will close the valve 19 an prevent excessive pressure.

The diaphragm as described may be used in connection with various forms of operating or coacting elements to produce sound as in a phonograph reprodu'cer or telephone, or to receive sound as in a phono raph recorder or microphone, but as here i lustrated it is used in a loud speaker in combination with. an electromagnetic coacting element described as follows surround the spool and act upon the arma ture at either end. A permanent magnet 24 secured to the housing 1 and contacting with said polepieces holds the several parts in proper position. The tension on the link 5 is counterbalanced by an elastic member, preferably a spongy body 25 such as rubber acting upon the armature 20. In turn the spongy body is acted upon by a spring lever 26 secured to the magnet by a screw 27 and adjustable by means of a screw 28. Having the proper pressure within the housing 1 the tension on the link 5 holds the armature firmly in contact with the spongy body 25- and the position of the armature between the -polepieces is adjustable by means of the screw 28.

The diaphragm being extremely light and practically nonelastic and the spongy body being comparatively dead in elastic reaction the combination has practically no resonant period and is therefore adapted to reproduce all sounds with a high degree of efficiency and accuracy.

The housing 1 is provided with a plurality of legs 29 which are secured to the base 30, and this base is made in the form of a reflector which may be made to reflect the sound equally in all directions.

I claim 1. An acoustic diaphragm operatively connected with an operating element, means to apply pneumatic pressure to one side of said diaphragm and a distorted spongy body adapted to counterbalance the pneumatic pressure by the force of distortion.

2. An acoustic diaphragm operatively connected with an operating element, means to apply pneumatic pressure to one side of said diaphragm and a compressed spongy body adapted to counterbalance the pneumatic pressure by the force of compression.

3. An acoustic diaphragm operatively connected with an electrically operated armature, means to apply pneumatic pressure to one side of said diaphragm, and a compressed spongy body acting upon said armature and adapted to counterbalance said pneumatic pressure by the force of compression.

4. An acoustic diaphragm operatively connected with an electrically operated armature, means to modify the pneumatic pressure on one side of said diaphragm and a distorted spongy body acting upon said armature and adapted to counterbalance the excess pressure.

5. Antacoustic device comprising a diaphragm operatively connected with a vibratile element, means to apply pneumatic pressure to one side of said diaphragm, and means to counterbalance said pressure, said means comprising a body practically devoid of a natural period of vibration.

6. An acoustic diaphragm having unequal pneumatic pressure on opposite sides and resilient means acting on said diaphragm to counterbalance the excess pressure, an operating element and means connecting said operatmg element with said diaphragm.

7. An acoustic diaphragm operatively connected with an electrically operated armature, means to apply difierent pneumatic pressures on opposite sides of said diaphragm, and an elastic member acting in connection with said armature and adapted to counterbalance the excess pressure on said diaphragm. I

8. An acoustic diaphragm comprising an inflated membrane and resilient means to counterbalance the pressure of inflation, and an electrically operated armature operatively connected with said diaphragm.

9. An acoustic diaphragm, operatively connected with an operating element, means to apply pneumatic pressure -to one side of said diaphragm, and a distorted elastic member adapted to counterbalance the pneumatic tortion.

10. An acoustic diaphragm, an electrically operated armature, a link operative- 1y connecting said armature with said diaphragm, means to apply pneumatic pressure to one side of said diaphragm, and a distorted elastic member adapted to counterbalance the pneumatic pressure by the force of distortion.

11. A loud speaker combination comprising an acoustic diaphragm having excess pneumatic pressure on one side thereof, an electrically operated armature, a link operatively connecting said armature with said diaphragm, and an elastic member adapted to counter-balance the excess pneumatic pressure on said diaphragm.

NATHANIEL BALDWIN.

pressure by the force of dis- 

